1. Technical Field
The present invention relates to integrated circuit designs in general, and, in particular, to a method and apparatus for distributing power in an integrated circuit having voltage islands. Still more particularly, the present invention relates to a method and apparatus for performing power routing on a voltage island within an integrated circuit chip.
2. Description of the Related Art
The concept of voltage islands is introduced into integrated circuit designs in order to integrate multiple design technologies on a same integrated circuit chip with increased performance and lower power consumption. The voltage island concept allows for one or more portions (islands) of an integrated circuit chip to be powered by both a chip-wide power source (VDDg) and other voltage island power sources (VDDi–VDDn). VDDg and VDDi–VDDn can be switched on and off in accordance with the operational demands of the integrated circuit. Typically, VDDg and VDDi–VDDn (as well as GND) are supplied to a voltage island from separate chip-wide power sources.
Generally speaking, a voltage island requires an isolated power supply grid structure from the remaining portion of a chip power grid. In order to generate an electrically robust power grid structure for voltage islands that do not contain electromagnetic or IR drop violations, off-chip and on-chip power supply sources need to be routed accordingly. Typically, off-chip power supply sources for voltage islands originate at either C4 ball grid array locations or wirebond locations, and on-chip power supply sources for voltage islands originate at voltage regulator macro pins.
There are many problems that need to be overcome in order to have efficient power connections from VDDg, VDDi–VDDn and GND to a voltage island. The problems that need to be overcome include how not to require an overabundance of power wires to anticipate the power needs of unplaced voltage islands, how not to restrict placement of power service terminals contained within the voltage island circuits because of a locally sparse power grid, how to avoid electromigration and IR drop violations and how to avoid blocked pins and other wireability issues.
The present disclosure provides an improved method for performing power routing on a voltage island within an integrated circuit chip.